Prior to the conception and development of the present invention, as is generally well known in the prior art, control of mixed concrete slump and pour are critical in providing the desired concrete for particular applications. Slump is a measure of the plasticity of fresh concrete relative to the amount it falls when a slump cone filled with concrete is lifted vertically. The industry testing standards are for example found in ASTM C143. Slump is generally increases with water content of the concrete. Concrete strength is inversely related to the water content in laboratory conditions. However, field conditions make control of the concrete variable more difficult, thus the necessity of obtaining the control of the slump is more critical.
It is known that sensors can be used in the mixing of concrete. For example U.S. Pat. No. 6,484,079 issued to Buckelew et al provides a global positioning satellite receiver to monitor the location of mixers. Similarly, U.S. Pat. No. 5,752,768 issued to Assh and U.S. Pat. No. 5,713,663 issued to Zandberg et al provides a system for control of mixing concrete using sensors. However, these inventions control the mixing using the rotation of the mixing drum in '768 and the torque on the mixer as it rotates in '663. This approach does not produce as good an approximation of the desired slump and does not provide the necessary information to estimate the amount of concrete in the mixer or the start and finish times of the pour.